Photographic silver halide emulsions stabilized with gallic acid or an alkyl ester thereof



United States Patent Office Patented July 22, 1969 3,457,079 PHOTOGRAPHIC SILVER HALIDE EMULSIONS STABILIZED WITH GALLIC ACID R AN ALKYL ESTER THEREOF Kenichi Koda, Shui Sato, Masayuki Shoono, and Haruo Hori, Tokyo, Japan, assignors to Konishiroku Photo gndustry C0,, Ltd., Tokyo, Japan, a corporation of apan No Drawing. Filed Dec. 22, 1965, Ser. No. 515,739 Claims priority, application Japan, Dec. 30, 1964, 39/74,371 Int. Cl. G03n 1/34 U.S. Cl. 96-109 5 Claims This invention relates to stabilized photographic compositions, and more particularly, it concerns with a photographic element, e.g., photographic film, paper or plate, bearing on a support a photosensitive layer containing gallic acid or its alkyl esters which may be generically referred to a gallic compound hereinafter.

In the art it is well known that photographic compositions, when stored for a long period after their preparation, sufiier from decrease in speed and formation of undesired fog. In order to prevent these adverse effects, a variety of stabilizers also have been proposed. Incorporation of the known stabilizers (e.g., azaindolizine), however, is disadvantageous because it often causes decrease in speed, and the demand in the art has been directed to develop a stabilizer which will permit to pervent fog without any adverse influence on photosensitivity.

It is accordingly one object of the present invention to provide a photographic composition which can resist to any undesired effect caused by storage over a long period of time.

Another object of the present invention is to provide a photographic element which is entirely safe from formation of fog.

Other objects, features, capabilities and advantages which are comprehended by the invention will be apparent from the specification and claims which follow.

The above-mentioned and other objects can be attained by incorporating a gallic compound as a stabilizer into a photographic composition.

We have now found that if the gallic compound is present in a photographic composition of the present invention, the said composition can be safely stored over a long period of time, without suffering from decrease in speed or formation of fog. In a typical embodiment of the present invention, the gallic compound may be incorporated into at least one of the gelatine-containing layers of a photographic element, such layers including emulsion layers, sublayers, internal layers, protective layers and backing layers. Another advantage of the present invention is that Where the gallic compound is added to a photographic emulsion during its digestion or ripening, it is possible to prevent fog formation and consequently to facilitate an increase of speed due to the digestion or ripening.

Suitable gallic compounds can be represented by the general formula HO- OH COOR wherein R represents hydrogen atom or a straight of branched alkyl radical containing 1 to 18 carbon atoms.

Typical compounds are gallic acid (M.P. 235 C. (decomp.)), methyl gallate .(M.P. 200 C.), ethyl gallate (M.P. 155 C.), n-propyl galate (M.P. 148 C.), isopropyl gallate (M.P. 124 C.), n-butyl gallate (M.P. 134 C.) isoamyl gallate (M.P. 146 C.), n-amyl gallate (M.P. 109 C.), n-hexyl gallate (M.P. 93 C.), n-heptyl gallate (M.P. 96 C.), n-octyl gallate (M.P. 96 C.), n-nonyl gallate (M.P. 97 C.), n-decyl gallate (M.P. C.), nhendecyl gallate (M.P. 97 C.), n-dodecyl gallate (M.P. 97 C.), n-tetradecyl gallate (M.P. 97 C.), n-hexadecyl gallate (M.P. 100 C.) and n-octadecyl gallate (M.P. 104 C.). Among these compounds, lower alkyl gallates can be readily prepared by the conventional techniques known by those skilled in the art, and higher alkyl gallates, for example, having more than ten carbon atoms can be prepared by the method described in Rec. Trav. Chim., 70, 277-284 (1951).

Incorporation of the gallic compound into a layer or layers of the photographic element-of the present invention can be made in the manner heretofore known per se :in the art. For example, if the gallic compound is to be present in an emulsion layer of the said element, it is possible to add the said compound into the emulsion at any time just before, during or after the second ripening of the said emulsion. Addition of the gallic compound at the stage after the second ripening of the emulsion is most preferred. Alternatively, the gallic compound may be added to a starting material for preparation of the emulsion, for example, gelatine. The amount added will vary depending on the type of emulsions, the degree of stabilization desired and the type of a layer to which the gallic compound is added, but it usually is within the range of from 0.003 g. to 3.0 g. per liter of the emulsion or coating solution. It is desirable to add this compound in solution dissolved in a suitable solvent, e.g., Water, methanol, ethanol, etc., if the addition is made to an emulsion.

Use of the gallic compound as a stabilizer does not adversely influence on sensitization of a photographic emulsion concerned. Thus, the photographic emulsion sensitized by way of gold-, sulfuror other chemical sensitization or optical sensitization can be successfully stabilized with the gallic compound. Any hardener, coating aid or other known photographic additives may be optionally used in combination with the gallic compound, without a significant loss of its stabilizing effect. Furthermore, it sometimes can provide desirable effect to facilitate an increase of speed because the said compound will prevent increased fog which frequently occurs accompanying to the sensitization. It is, of course, true that decrease of speed and increase of fog during storage of the emulsion also can be prevented by using the gallic compound.

Still another advantage of the present invention is that fog and desensitization both which frequently occur during the storage of a color photographic material containing color formers in the emulsion can be effectively prevented by using the gallic compound.

The emulsion to which the gallic compound has been added can be applied to a suitable support in the manner heretofore known per se in the art, e.g., coating or pouring. Suitable supports include films, papers and glass plates. For example, films of the types, such as cellulose esters, e.g., cellulose triacetate; polyesters obtained by the polycondensati'on of phthalic, isophthalic or terephthalic acid with a dihydric alcohol, e.g., polyethylene terephthalate, poly [cyclohexane 1.4 dimethylol]terephthalate, etc.; and polycarbonates including those obtained by the polycondensation of bis-phenol A with carbonic acid, are suitable.

The following examples describe certain ways in which the principle of the invention has been applied, but are not to be construed as limiting its scope.

3 EXAMPLE 1 A silver bromo-iodide emulsion useful for high speed negatives and containing 3 mol percent of silver iodide is prepared according to neutral process. This emulsion 4 ripening, the emulsion is optically sensitized by addition of 9-methyl-3,3'-diethyl seleno carbocyanine bromide in the amount of 50 mg. per liter of the emulsion. The emulsion is divided to nine portions, one of which is used for preparation of control film without any stabilizer and is added With a gold-sensitilef and then Subjected to 5 the other seven used after the addition of the gallic comond ripening at a temperature of 60 C. for 75 minutes. pounds specified in the respective columns of Table II. After the said ripening, the emulsion 18 divided to eleven Th remaining one portion i dd d ith the same known portions, one of which is used for preparation of control stabilizer as in Example 1. Each portions are prepared film without any stabilizer and the other nine used after to fo film T t pieces ut f om the films are then the addition of the gallic Compounds spficlfied 1n e subjected to a comparative test in the same manner as in respective columns of Table I. The remaining one por- Example 1. The results obtained are set forth in Table II.

TABLE II Incubated at 50 C. Just aiter Iueubated at 55 C. and 80% RH for 2 preparation for 2 days after days after oi the film preparation preparation Amount used Relative Fog Relative Fog Relative Fog Compound (mg/1.) speed speed spee Control 0 100 0. 09 67 0. 34 90 0. 12 Gallic acid 135 101 0. 10 93 0. 12 90 0. 10 Ethyl gallatenn 160 96 0. 09 90 0. 12 100 0. 00 n-Propyl gallate 170 100 0. 09 90 0. 0B 101 0. 10 n-Butyl gal1ate. 180 100 0. 09 9e 0. 11 100 o. 10 n-Heptyl gallate. 210 100 0. 09 89 0. 10 110 0. 11 n-Dodeeyl gallate. 270 102 0. 10 98 0. 11 100 0. 11 n-Hexadecylgallat 310 103 0. 10 99 0. 12 103 0. 11 Known stabilizer- 150 96 0. 09 84 0.08 73 0. 08

tion is added with 5-methyl-7-hydroxy-1,3,4-triazaindolizine which is the known stabilizer. Each portions are prepared to form films. Each films are cut into three pieces, one of which is immediately subjected to the later specified sensitometric test, and the second and third pieces are stored at 55 C. for 2 days or at 50 C. under a relative humidity of 80% for 2 days before the same test. Samples of these film coatings were then exposed in an intensity-scale type sensitometer and developed for five minutes in a developer of the following formulation:

Grams Metol (monomethyl-p-aminophenol sulfate 1.5 Sodium sulfite (anhydrous) 25.0 Hydroquinon 3.0 Sodium carbonate (monohydrate) 15.0 Potassium bromide 0.5

Water to make 1.0 liter.

The developed samples were stopped with dilute acetic acid and then fixed, washed and dried. The results are set forth in Table I.

COOR

wherein R represents hydrogen atom or a straight or branched alkyl radical having 1 to 18 carbon atoms.

TABLE I Incubated at C. Just aiter Incubated at 55 C. and RH for 2 preparation for 2 days after days after of the film preparation preparation Amount used Relative Fog Relative Fog Relative Fog Compound (mg/l.) speed speed speed Control. 0 0. 14 74 0. 43 142 0. 22 Gallic acid- 135 98 0. 12 98 0. 18 115 0. 11 Ethyl gallat 160 100 0. 10 100 0. 16 109 0. 10 n-Propyl gallate 170 95 0. 10 92 0. 15 107 0. 10 Isoamyl g 190 09 0. 12 95 0. 17 110 0. 10 n-Hoxyl gallate 200 100 0. 12 06 0. 16 0. 12 n-Octyl gallate 220 98 0.11 92 0. 16 115 0. 11 n-Decyl gallate 250 100 0. 12 06 0. 17 0. 10 n-Tetradecyl gallate 290 100 0. 12 97 0. 16 115 0. l1 n-Oetadecyl gallate 330 98 0. 13 99 0. 18 112 0. 11 Known stabilizer- 80 0. 13 76 0. 12 61 0. 09

In this test, photographic speed which is a reciprocal of 65 the exposure to give an optical density of 0.5 above fog density, is expressed as relative speed to that of unstored control film, which is rated as 100. The data of Table I clearly indicates that alkyl gallates are useful for prevention of undesired fog formation during incubation.

EXAMPLE 2 The photographic emulsion used in Example 1 is sub- -jected to second ripening in the same manner as in Example l. Five minutes before completion of the second 5 having incorporated therein a stabilizing compound of the formula COOR to 3.0 g. per liter of the emulsion in the coating solution used in the preparation of the emulsion layer.

References Cited UNITED STATES PATENTS wherein R represents hydrogen atom or a straight or 10 NORMAN GTORCHINPrimary Examiner branched alkyl radical having 1 to 18 carbon atoms, the amount of said stabilizing compound being equal to 0.0003

R. E. FICHTER, Assistant Examiner 

1. A LIGHT-SENSITIVE, PHOTOGRAPHIC SILVER HALIDE EMULSION COMPRISING GELATIN HAVING LIGHE-SENSITIVE SILVER HALIDE DISPERSED THEREIN AND CONTAINING A STABILIZING AMOUNT OF A COMPOUND OF THE GENERAL FORMULA 